This invention relates generally to load-carrying truck boxes of the type having a hinged sideboard and more particularly to a mechanism for opening and closing such sideboards.
Many trucks that have been in common use in farming operations for a number of years are adapted to haul a variety of farm commodities such as sugar beets, silage, grain and the like. These trucks are typically referred to as beet trucks and are characterized in that they have a load-carrying box that includes a pair of sideboards hinged adjacent the bed of the truck box. Loads carried by such trucks are typically dumped by first moving one of the hinged sideboards from an upright or closed position to a lowered or open position and by then tilting the truck box in the direction of the lowered sideboard to effect dumping of the remainder of the load. In the ordinary type of beet truck now commonly used, it is necessary for the driver to leave the driver's seat on arrival at his load-dumping destination, release a chain at each end of the sideboard that is used to hold the sideboard in the closed position, and lower the sideboard by hand. After unloading the truck the driver must then manually raise the sideboard and secure the chain at each end of the sideboard before returning to the driver' s seat. This manual lowering and raising of the sideboard represents an inconvenience to the truck driver and, in addition, poses a risk of injury in the event the force presented by the load is too great to allow the driver to hold the sideboard while lowering it.
Several attempts have been made to automate the lowering and closing of truck sideboards. Exemplary of these prior art attempts are the teachings of U.S. Pat. Nos. 4,052,106 and 3,977,718. While some degree of automation is achieved by these prior art inventions, they variously suffer the disadvantages of not providing a positive lowering and raising action while at the same time permitting the sideboard a degree of freedom of movement based on the force exerted by the load and of not providing a locking mode when the sideboard is in the closed position to positively hold it in that position in the event of loss of hydraulic pressure to the cylinders that exert the actuating force.
Accordingly, it is the principal object of the present invention to provide an automatic, self-locking sideboard lift and dump mechanism that permits the sideboard a degree of freedom of position during lowering as a function of the force exerted thereon by the load.
These objects are accomplished in accordance with the illustrated preferred embodiment of the invention by employing dual lift mechanisms, one adjacent each end of a sideboard. Each lift mechanism includes a hydraulic cylinder, a rotatable shaft having lever arm extensions at each end thereof, a corner bracket mounted to the sideboard, and a linkage arm articulately coupling a pivot point on the corner bracket with one of the lever arm extensions.